1. Field of the Invention
The present invention relates to a feeding apparatus, more specifically, relates to a feeding apparatus for feeding roll paper.
2. Description of the Related Art
Recently, digital cameras have been widely used to capture many images. In order to print the many pieces of image data effectively, it is becoming necessary to print more sheets within a shorter time period and to eliminate the job of cutting a margin of a printed product. Therefore, increasing the rate of printing and a marginless of the printed product are required, not only for professional use printers, but also for a house hold use printer. In view of the above, a roll paper type printer comes to be employed also in the house hold use printer and thus a paper feeding mechanism for the roll paper is required also in the house hold use printer.
Conventionally, a method for causing a user to insert a leading edge of the roll paper into, or pinch the leading edge of the roll paper, a paper feeding roller or a paper guide is generally known as a roll paper loading method. Recently, such a method is frequently used, as a paper feeding mechanism of the roll paper that does not place a burden on a user, that the roll paper in which a roll paper shaft is inserted is loaded into a paper feeding unit, and a seal for sealing a leading edge of the roll paper is removed to complete the loading processing. The roll paper shaft loaded by the user is pressed against the paper feeding roller using a pressurizing mechanism provided on a printer main body or the feeding apparatus in order to cause the paper feeding roller to contact with an outer circumference of the roll paper under pressure and to cause the paper feeding roller to rotationally drive in a sheet feeding direction to rotate the roll paper. Then, a paper feeding mechanism that picks up a leading edge of the outermost circumference of the roll paper by a pick-up member to feed the roll paper is used.
For example, Japanese Patent Application Laid-Open No. 2006-306511 discusses a cassette including an urging mechanism for urging a roll paper on a paper feeding roller and a pick-up member contactable with the outer circumference of the roll paper in order to pick up the leading edge of the roll paper. Japanese Patent Application Laid-Open No. 2006-306511 further discusses a mechanism for extracting the roll paper by picking up the leading edge of the roll paper according to a press-contact rotation of the paper feeding roller after the roll paper is loaded to a main body. According to the mechanism, the roll paper shaft is movable in a direction toward the paper feeding roller even with a small amount of remaining roll paper after the roll paper is withdrawn, so that the roll paper can be stably fed while an unrolling of the roll paper is controlled. Even in a case where an entire length of the roll paper becomes longer and thus the roll paper itself becomes heavier, which tends to exert an adverse effect in feeding paper, a pick-up operation can be stably performed by a positional relationship in a vertical direction between a pick-up guide and the roll paper being set such that a tip end of the pick-up guide is positioned above the rotational shaft of the roll paper.
In Japanese Patent Application Laid-Open No. 11-11750, the roll paper is rotatably supported and the pick-up guide for separating the leading edge of the roll paper is urged such that the pick-up guide contacts the outer circumference of the roll paper. The tip end of the pick-up guide is always positioned on the outer circumstance of the roll paper following a change of an outer diameter of the roll paper. The roll paper is rotatably driven, the picked up leading edge of the roll paper passes between an outer circumferential guide member and the pick-up guide, and the roll paper is conveyed from the outer circumferential guide member to a paper guide board positioned at a downstream side of the outer circumferential guide member. In order for the leading edge of the roll paper to be securely guided to a paper guide board, a distance in a sheet thickness direction of an opening portion of the paper guide board is made wider than a distance of an exit formed between the pick-up guide and the outer circumferential guide member. Further, a slope that is gentle in an up-and-down direction is provided to enable guiding of the leading edge of the roll paper to the downstream side.
A smaller size is desired in a field of the house hold use printer. However, in the above described conventional art, the leading edge of the roll paper is guided by the paper guide for conveying the roll paper from the paper feeding unit to a print unit, which adversely effects on downsizing of the printer. In a case where an inner diameter of the roll paper is made smaller for the purpose of downsizing of the printer, a curling degree that the roll paper originally has and an amount of change in the curling degree between the innermost circumference portion and the outermost circumference portion become larger. Therefore, when the roll paper is conveyed from the pick-up guide member to the print unit, a position of the leading edge of the roll paper varies according to an adverse effect of the diameter and/or the curling degree. Therefore, it is required to guide the varied positions of the leading edge to a desirable sheet feeding direction so as to avoid jamming of the roll paper. The diameter of the roll paper becomes smaller as the number of sheets of the feeding paper becomes larger. Thus, the curling degree of the roll paper is the smallest in the start of using the roll paper and becomes gradually larger as using the roll paper. The positions of the leading edge of the roll paper coming out through a guiding surface of the pick-up guide according to the curling degree of the roll paper also change gradually. In order to securely guide the leading edge of the roll paper thus varied, a paper guide having a gentle slope is required.
FIG. 8A illustrates a conventional example of a paper feeding unit including a paper guide. In a case where the paper feeding unit includes the paper guide, an installation space is required for an installation surface and prevention of deformation of the paper guide. As illustrated in FIG. 8A, since a paper guide 801 is provided on the paper feeding unit, a distance between a roll paper accommodating unit 802 and a pinch roller 803 and a grip roller 804 for conveying the paper during printing cannot be closer. Therefore, there is an issue in downsizing the paper feeding unit.
If the paper guide 801 is eliminated, when an end of the roll paper having smaller diameter is fed, as illustrated in FIG. 8B, the curling degree of the roll paper becomes larger. With a shape of the conventional pick-up member 805, the leading edge of the roll paper curls up after the roll paper passes through a rotational center 805a. There is an issue that the roll paper comes into a space between the pick-up member 805 and the pinch roller 803 to disable the guiding of the leading edge to a space between the pinch roller 803 and the grip roller 804. To realize downsizing without impairing a paper feeding function is the issue to be solved.